Electromagnetic bell striker



Oct. 3, 1950 y l.. c. KING ELEcTnouAGNEnc .BELL Smm Filed sept. 2 7,1947 L Y 49 4f 4? I 414, f/ ff l f f Patented Oct. 3, 1950 UNITED STATESPATENT OFFICE ELECTROMAGNETIC BELL STRIKER Louis C. King, Quincyy Mass.

Application September 27, 1947, Serial No. 776,548

1 Claim.

The present invention relates to the general field of electric bells,but is of special character and is adapted to perform services of whichno other electric bells within my knowledge are capable. There is acrying need for Warning bells which will make a noise loud enough andpenetrating enough to be heard at a far enough distance from unguardedrailroad crossings to giveV a safe warning of approaching trains, and tobe sharply heard over the din and racket of large machine shops,Shipyards, and other localities where noisy machines are in operation,the hammering and the lifting and dropping of heavy weights are goingon, or othery conditions exist which tend to distract the attention ofpersons in the vicinity. For instance, heavy mobile machines, such asgantryr cranes which travel on tracks, are employed in Shipyards andlarge shops, and such machines when once started in motion cannot bequickly stopped. People `who may be in the wayv of such a moving machineand do not see it coming are liable to be killed or seriously hurt. Thenoise in the places where such cranes are used is generally so loud andconfused as to smother Warning shouts and the sound of any such Warningbells or gongs as have heretofore been available on the market.

The purpose of the present invention is to provide an automatic warningbell for the uses above indicated and many other` uses, including meansfor striking the bell with such force as to make la loud and penetratingringing noise, with repeated blows at intervals sufficiently far apartto permit full amplitude of vibration of the bell and compel theattention of all who are able to hear it. A related object is to providein combination with the foregoing, convenient and' easily operated meansfor adjusting and varying the frequency rate of the striking means.Further objects are to furnish a rugged, durable apparatus for thepurpose set forth capable of long continued effective use under severeconditions of mechanical shock and vibration and when activated byelectric current of relatively high voltage.

These objects are accomplished by the apparatus or device described inthe following specification and illustrated in the drawings. Theinvention consists in the novel features and combinations embodied insaid device, and iny all equivalents thereof and their fundamentalrprinciples.

In the drawings,

Fig. 1 is a plan View of an electro-magnetic bell striker embodying thisinvention;

Fig. 2 is a longitudinal axial section of the striker apparatus taken online v2-2 of Fig. 1;

Fig. 3 is a partial cross section taken on line 3-3 of Fig. 2;

Fig. 4 is a side elevation of the parts shown in Fig. 3 and a sectiontaken on line 4 4 of lthat figure;

Fig. 5 is a view similar to Fig. 4, but showing the, circuit breaker inopen circuit position and the actuating means therefor in acorresponding position. 4

Like reference characters designate the same parts wherever they occurin all the gures.

The main parts of the striker apparatus include a base II of insulatingmaterial, a solenoid coil or winding I2, a stationary holder I3 for oneof the terminals or contacts of an electric circuit making and breakingdevice, and a movable contact carrier or circuit interrupter I4; allsuitably mounted on and secured to the base Il. Y

The coil I2 is wound as a self-contained unit on a spool or sleeve I2a.which surrounds a tube I5 made of nonmagnetic material, for instancebrass. This tube is supported by plates or brackets I6 and I1 which havefeet I8 turned toward one another and secured to the base I I by screwsI9; the tube thus constituting both a support for the coil I2 and aguideway for the solenoid core 20. It protrudes at both ends from thebrackets sufficiently to be adequately supported and to serve thepurposes later explained. It may be connected to one or both brackets bysolder or other means effective to hold it securely against displacementbut which permit easy disconnection in case need arises to substitute anew or different coil.

The rcore 20 is made of iron or mild steel with a free sliding iit inthe tube I5. It carries on the end which, for the purposes of thisspecification, is called the forward end, an extension 2l of nonmagneticmetal which, in turn, carries on its forward-end a striker head 22, ofhard steel or other material suitable to withstand wear and to cause aloud ringing of a bell against which it may be caused to strike. Ahelical spring 23 surrounds the core extension 2l and is confined undercompression between a shoulder 24 `on the core and a washer 25 whichlies against an internal shoulder 26 at the forward end of tube I5.Spring 23 is stiff enough and long enough to retract the core as rapidlyas permitted by the timing regulator later described, and to such extentthat the mag netic core is brought to a position of magnetic Vunbalancewith respect to the coil, when the coil is deenergized.

It is not so strong, however, as to prevent the core from being advancedsuddenly and with accelerating speed by magnetic force when the coil isenergized.

The stationary contact holder I3 is a rigid bracket of electricallyconductive metal, such as brass or steel, having a foot portion which issecured to the base I I by a screw 21, and an upright portion whichsupports a contact piece or circuit terminal 29. This terminal has ascrew threaded shank which passes through an internally threaded hole inthe upstanding part of the holder I3, whereby it may be rotated toadjust its contact extremity forward or back. A lock nut 39 or, ifdesired, a pair of lock nuts, is applied to the threaded shank to securethe terminal in its various adjusted positions.

The circuit interrupter I4 carries a contact or terminal 3I arranged tocooperate with the contact 29. It is a plate or bar of electricallyconductive metal, to which the terminal 3| is secured conductively,mounted 'on a base block 32 of electrically conductive material which issecured to the base I I; connection being made between the interrupterand base block by a pivot pin 33 passing through the lower end of theinterrupter and through posts 34 which rise from the block and embracethe lower end of the interrupter.

The pivot 33 is at a substantial height above the base II, whereby thelinear movement imposed on the interrupter I4 causes it to swing througha Wide angle. A helical tension spring 35 is connected to the base blockby a pin 38 at a substantial distance below the pivot, and to theinterrupter I4 by a pin 31 at a, substantial distance above the pivot.The interrupter is so located that when its contact piece 3I bearsagainst contact piece 29, the spring is at the same side of the pivot 33as contact 29 and exerts force tending to hold the movable contact incircuit closing position. But the interrupter I4 is free to move awayfrom the contact 29 far enough to bring the spring to the opposite sideof the pivot, its movement in that direction being limited by anysuitable stop means, here illustratively indicated as a post 38 risingfrom the base block 32 beside the interrupter to a height above pivot33.

The position established by this stop is shown in Fig. 5. Thus spring 35is adapted to hold the movable member of the circuit closer againstaccidental displacement when in the open circuit position, and to bringit rapidly into circuit .closing position when it has been moved pastthe dead center from the position shown in Fig. 5.

For thus moving the interrupter I4 past the dead point in eitherdirection, shifter members 4D and 4I and an intermediate spacer 42, allof insulating material, are connected with the solenoid core 2U by a rod43 which passes through them and is secured to the rear end of the corein alinement therewith. These shifter members are conveniently made asdisks, which may be reinforced by metal disks 44 and 45, respectively,at their outer faces. They are located so as to embrace a projection I4Ion the side of the upper end portion of the interrupter I4 and to engageand move the interrupter when the core is moved endwise. They are spacedapart and located with respect to the limits of movement of the core andto the location of the interrupter so that the shifter' 40 will engagethe interrupter and shift it from the circuit closing position toslightly beyond its dead point with respect to the pull of spring 35just before the core reaches the end of its forward movement, that is,its position when its striker head 22 hits the bell. The other shiftermember 4I is located to engage the interrupter I4 during thespring-retracted movement of the core and to bring the interrupter pastits dead' point when the core reaches its prescribed limit of rearwardmovement. Thus the core, in its back and forth movements, causes thecircuit of the solenoid to be alternately made and broken.

The effectiveness of my striker mechanism for achieving its intendedpurpose depends principally on two main features. One is the winding ofthe solenoid to exert a powerful magnetic pull when energized. The otheris an adjusting means by which the striking frequency of the core may beregulated and made sufficiently slow to afford appreciable intervalsbetween successive strokes. The regulator in the embodiment here showncomprises a piston 46 carried by the solenoid core on the remote end ofrod 43 in rearward extension from the shifter member 40, and containedin a cylinder 4'I. Such cylinder may be formed in a block ofnon-conductive material secured to the base I I, and such block may bedisposed with a portion in the path of the disk 44 located to serve as astop for establishing the rearward limit of movement of the core.

Piston 46 includes a flexible cup washer, the rim 48 of which facesrearwardly (with respect to the striking movement of the core) towardthe head wall 49 of the cylinder. A vent passage 5U leads from the headend of the cylinder and is controlled by a needle valve 5I so as toregulate the-effective area of the passage. The opposite end of thecylinder is open to the atmosphere so as to admit air freely to thecylinder space back of the cup washer when the core is magneticallyimpelled. Thus the piston makes no appreciable resistance to the outwardor striking movements of the core, but it prevents escape of air fromthe open end of the cylinder when the core is retracted, and so retardsthe speed of retracting movements thereof to the speed of escape of airthrough the restricted channel past the valve 5I. By adjustment of thevalve, any desired striking frequency, less than the maximum possible,can be obtained.

The cup washer 48 is, in effect, a valve which permits substantiallyfree passage of air, or passage with very little resistance, into thespace between the piston and closed end of the cylinder when the pistonis moving outwardly, but confines the air in such space when the pistonis moving toward the cylinder head. Other valve means having the sameessential function and effect are within the range of equivalents ofthis phase of the invention.

The core 2U has a sliding fit in the tube I5, as previously noted. It islubricated by the disk or pad 52 which surrounds the rear end of tubeI5, protruding from bracket I5, and is saturated with oil. Holes 53 inthat part of the tube that is surrounded by the disk 52 permit flow ofoil between the rubbing surfaces of the core and tube.

The electric circuit for this apparatus comprises a line wire 54connected with the contact terminal 29 by the screw 2'I, which serves asa binding post, and a line wire 55 connected with one terminal of thesolenoid winding. The other terminal of this winding is connected withthe block 32 by a conductor 56 and binding screw 5'I. A conductive post58 rises from block 32 at the opposite side of interrupter I4 from thestop post 38 and supports a spring strip 59 of conductive metal, whichextends upwardly and is curved over so that its extremity is brought inrubbing contact with the upper end of the interrupter I4 when the latteris in and near the position where the contact 3l bears on contact 29. Acondenser 60 is connected across the circuit breaker terminals tosuppress the arc which tends to form when the movable contact iswithdrawn from the fixed contact.

The apparatus thus described is mounted, together with s, bell 6l, on aframe or supporting structure 62 of any suitable character. The bell issupported by a post 63 with a portion of its rim in the path of thestriker head 22 at a distance from the solenoid short of the possiblelimit of forward movement of the striker, and preferably as nearly aspossible to the point reached by the striker head when the core hasattained its anaxmum velocity. IIhe bell here shown is of the gong type,but obviously any other type of bell may be used.

The striker mechanism is set in operation by closing a switch in themain circuit. The coil l2 is thereby energized, which causes the core tomove forward with a rapid acceleration. When it has nearly attained itsmaximum velocity, but before it has struck the bell, the shifter collar40 engages the interrupter i4 and suddenly withdraws the contact 3i fromcontact 29. Continuing movement of the core before striking the bellpropels the interrupter beyond its dead center position, so that it isheld by its spring 35 away from the stationary contact until return ofthe core. During return movement, which is retarded by the piston 45,and when the core has nearly reached its limit of return mov-ement, theinterrupter is moved by the shifter lll rearwardly past its dead point,and spring 35 then causes it to close the circuit until the next forwardstroke has progressed to the point previously described.

In addition to the features previously described, it should be notedthat the base block 32 for the circuit interrupter, and the holder I3for the stationary contact, are located on the insulatn ing base l! withspaces of substantial width between them and between each o-f them andthe nearer supporting standard (i6) of the solenoid. This disposition ofthese electrically conductive members affords ample insulation betweenparts which are at different electrical potentials and between which thedifference of potential may at times be very great. For instance, whenthe current is shut off from the solenoid coil, the magm .netismsubsides instantly, and the contracting lin-es of magnetic force cut thewindings of the coil and generate a high counter electromotive forcewhich is impressed on the bracket i6. Still greater inductive reactancesare developed from operation of the electrical equipment of machines,such as cranes, on which'the bell may be installed. The separationbetween this bracket and parts of the circuit interr'upter preventsjumping of current from the bracket to the circuit controller underdifference of potential of as much as 1800 volts.

Apparatus made in accordance with the foregoing disclosure has proved tobe singularly effective in giving warning in situations such as thosementioned in the introductory part of this specilcation. It deliverspowerful impacts to the bell at intervals frequent enough to afford aninsist ent warning, but separated suiciently to enable the bell to ringwith full resonance. By way of illustration I may say that ya desirablefrequency of striking is two or three strokes :per second, and thesefrequencies are well within the limits of the speed regulating device.Slower frequencies than these may be obtained if desired.

This application is a continuation-impart ofr my application Serial No.572,113, filed January 10, 1945, entitled Electro-Magnetic Bell Striker,now abandoned.

What I claim is:

A bell striker mechanism comprising a support? ing structure, a solenoidmounted thereon, a core movable through the solenoid, a spring acting onsaid core normally holding it in a. position of magnetic unbalance withrespect to the solenoid and with one end projecting therefrom, a pistonvcarried by the said projecting end of the core, a cylinder in which saidpiston is contained for axial movement, having s, closed end remote fromthe solenoid and a valve controlled vent opening into the space adjacentto said closed end, the piston having a valve portion disposed to permitilow past it of air into the space between it and the closed end of thecylinder when moving away from such closed end and to prevent escape ofair when the piston moves toward the closed end, a make and break devicein circuit with the solenoid winding, means carried by the core forcausing said device to complete the circuit when the core is projectedby its spring, and to break the circuit when the core is shifted bymagnetic iluX, and a strike extension on the opposite end of the corefrom the piston arranged to be projected from the solenoid when saidcore is advancedV by the magnetic effect of the energized solenoid.

LOUIS C. KING.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 866,471 Hunter Sept. 17, 19071,117,484 Dunham Nov. 17, 1914 1,284,930 Roberts Nov. 12, 1918 1,619,677Pierce Mar. 1, 1927 1,737,387 Redmond Nov. 26, 1929 1,983,068 CardoneDec. 4, 1934 1,990,566 Rarnsden Feb. 12, 1935 2,434,070 Gross Jan. 6,1948

